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21 <a href="/"><h1 id="title">i3 - improved tiling WM</h1></a>
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31 <h1>The multi-monitor situation</h1>
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32 <span id="author">Michael Stapelberg</span><br />
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33 <span id="email"><tt><<a href="mailto:michael+i3@stapelberg.de">michael+i3@stapelberg.de</a>></tt></span><br />
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34 <span id="revdate">March 2010</span>
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36 <div id="toctitle">Table of Contents</div>
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41 <div class="sectionbody">
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42 <div class="paragraph"><p>…or: oh no, I have an nVidia graphics card!</p></div>
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46 <h2 id="_the_quick_fix">1. The quick fix</h2>
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47 <div class="sectionbody">
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48 <div class="paragraph"><p>If you are using the nVidia binary graphics driver (also known as <em>blob</em>)
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49 you need to use the <tt>--force-xinerama</tt> flag (in your .xsession) when starting
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50 i3, like so:</p></div>
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51 <div class="listingblock">
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52 <div class="title">Example:</div>
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53 <div class="content">
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54 <pre><tt>exec i3 --force-xinerama -V >>~/.i3/i3log 2>&1</tt></pre>
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59 <h2 id="_the_explanation">2. The explanation</h2>
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60 <div class="sectionbody">
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61 <div class="paragraph"><p>Starting with version 3.ε, i3 uses the RandR (Rotate and Resize) API instead
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62 of Xinerama. The reason for this, is that RandR provides more information
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63 about your outputs and connected screens than Xinerama does. To be specific,
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64 the code which handled on-the-fly screen reconfiguration (meaning without
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65 restarting the X server) was a very messy heuristic and most of the time did
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66 not work correctly — that is just not possible with the little information
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67 Xinerama offers (just a list of screen resolutions, no identifiers for the
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68 screens or any additional information). Xinerama simply was not designed
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69 for dynamic configuration.</p></div>
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70 <div class="paragraph"><p>So RandR came along, as a more powerful alternative (RandR 1.2 to be specific).
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71 It offers all of Xinerama’s possibilities and lots more. Using the RandR API
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72 made our code much more robust and clean. Also, you can now reliably assign
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73 workspaces to output names instead of some rather unreliable screen identifier
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74 (position inside the list of screens, which could change, and so on…).</p></div>
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75 <div class="paragraph"><p>As RandR has been around for about three years as of this writing, it seemed
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76 like a very good idea to us, and it still is a very good one. What we did not
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77 expect, however, was the nVidia binary driver. It still does not support RandR
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78 (as of March 2010), even though nVidia has announced that it will support RandR
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79 eventually. What does this mean for you, if you are stuck with the binary
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80 driver for some reason (say the free drivers don’t work with your card)? First
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81 of all, you are stuck with TwinView and cannot use <tt>xrandr</tt>. While this ruins
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82 the user experience, the more grave problem is that the nVidia driver not only
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83 does not support dynamic configuration using RandR, it also does not expose
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84 correct multi-monitor information via the RandR API. So, in some setups, i3
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85 will not find any screens; in others, it will find one large screen which
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86 actually contains both of your physical screens (but it will not know that
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87 these are two screens).</p></div>
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88 <div class="paragraph"><p>For this very reason, we decided to implement the following workaround: As
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89 long as the nVidia driver does not support RandR, an option called
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90 <tt>--force-xinerama</tt> is available in i3. This option gets the list of screens
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91 <strong>once</strong> when starting, and never updates it. As the nVidia driver cannot do
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92 dynamic configuration anyways, this is not a big deal.</p></div>
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96 <h2 id="_see_also">3. See also</h2>
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97 <div class="sectionbody">
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98 <div class="paragraph"><p>For more information on how to use multi-monitor setups, see the i3 User’s
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103 <div id="footnotes"><hr /></div>
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105 © 2009-2011 Michael Stapelberg, <a href="/impress.html">Impressum</a>
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